The cold-induced transcription factor bHLH112 promotes artemisinin biosynthesis indirectly via ERF1 in Artemisia annua

Abstract

Basic helix-loop-helix (bHLH) proteins are the second largest family of transcription factors (TFs) involved in developmental and physiological processes in plants. In this study, 205 putative bHLH TF genes were identified in the genome of Artemisia annua and expression of 122 of these was determined from transcriptomes used to construct the genetic map of A. annua. Analysis of gene expression association allowed division of the 122 bHLH TFs into five groups. Group V, containing 15 members, was tightly associated with artemisinin biosynthesis genes. Phylogenetic analysis indicated that two bHLH TFs, AabHLH106 and AabHLH112, were clustered with Arabidopsis ICE proteins. AabHLH112 was induced by low temperature, while AabHLH106 was not. We therefore chose AabHLH112 for further examination. AabHLH112 was highly expressed in glandular secretory trichomes, flower buds, and leaves. Dual-luciferase assays demonstrated that AabHLH112 enhanced the promoter activity of artemisinin biosynthesis genes and AaERF1, an AP2/ERF TF that directly and positively regulates artemisinin biosynthesis genes. Yeast one-hybrid assays indicated that AabHLH112 could bind to the AaERF1 promoter, but not to the promoters of artemisinin biosynthesis genes. Overexpression of AabHLH112 significantly up-regulated the expression levels of AaERF1 and artemisinin biosynthesis genes and consequently promoted artemisinin production.

Enhancing artemisinin content in and delivery from Artemisia annua: a review of alternative, classical, and transgenic approaches

“…These transcription factors act as transcriptional activators of artemisinin biosynthetic genes including ADS, DBR2, CYP71AV1, and ALDH1 (Liu et al 2017). Expression of these genes occurs in a coordinated manner under low temperature, hinting at the participation of certain specific transcription factors in regulating artemisinin biosynthesis under such conditions (Xiang et al 2019). The bHLH transcription factors, mainly ICEs (inducers of CBF expression) induced by the cold are crucial for cold stress tolerance (Fursova et al 2009), but their role in terpenoid biosynthesis has not been validated.…”

Genome-wide survey of the bHLH super gene family in Brassica napus

“…The substantial increase in the number of bHLH genes was concomitant with their increased involvement in diverse physiological and developmental processes, with the majority being involved in metabolism and development. For instance, Arabidopsis AtbHLH045/MUTE controls sequential cell fate [11]; SlbHLH22 in tomato promotes early flowering and accelerates fruit ripening [12]; the bHLH transcription factor SPATULA (SPT) homologs are required for either carpel development or are involved in endocarp margin development in Arabidopsis and Prunus persica [13,14]; the bHLH transcription factor MYC2 homologs regulate sesquiterpene and artemisinin biosynthesis in various species such as Aquilaria sinensis and Artemisia annua [15,16]. Meanwhile, some bHLHs are related to abiotic stress response, including cold, drought, and salt stresses.…”

Transcriptome Analysis of Light-Regulated Monoterpenes Biosynthesis in Leaves of Mentha canadensis L.

“…The overexpression of transcription factors that target and positively control multiple monoterpene biosynthesis, or the suppression of the expression of negatively controlled TFs, could also each represent metabolic engineering strategies for improving essential oil yields. Previously, researchers have elucidated the regulatory roles of several genes encoding the WRKY [ 27 , 28 , 29 ], MYB [ 30 ], bHLH [ 31 ], AP2/ERF [ 32 , 33 ], and bZIP [ 8 ] classes of TFs in specialized terpenoid biosynthesis. Using RNA-Seq in Solanum lycopersicum , SlMYC1 was identified and shown to transiently transactivate the terpene synthase promoters in Nicotiana benthamiana leaves [ 34 ].…”